The interaction between computing devices and users continues to improve as computing platforms become more powerful and able to respond to a user in many new and different ways. A user is no longer required to only type on a keyboard in order to control applications and input data. The development of a graphic user interface system, like that provided by Microsoft Corporation's WINDOWS® operating system, has greatly improved the ease with which a user can interact with a computing device by enabling a user to input actions and make selections in a more natural and intuitive manner. The ease with which a user can input control actions is particularly important in applications where the need to provide input quickly and efficiently is important, e.g., video games, virtual environments, file/folder management, etc. In the past, users typically interacted with virtual environments by manipulating a mouse, joystick, wheel, game pad, track ball, or other user input device to carry out some operations as defined by the software program that produces the virtual environment.
One form of user input employs displays that are responsive to the touch of a user's finger or a stylus. These touch-sensitive devices are becoming more common in computing systems. They are very convenient as they allow a user to make natural gestures familiar to the user in other contexts, such as by entering handwriting using a stylus. Many of these devices also allow input to be provided by non-stylus objects, such as a user's fingertip. Touch-sensitive displays can be pressure activated, respond to electrical capacitance or changes in magnetic field intensity, employ surface acoustic waves, respond to changes in brightness by detecting light or shadow from a finger or object over the display, or respond to other conditions that indicate the location of a finger or stylus on the display. As a result, a user can more directly interact with an application or operating system on a computing device. For example, the user may touch the touch-sensitive display with a single finger to select a virtual object and then drag the selected virtual object to a new position on the touch-sensitive display. The term touchscreen or interactive display device will be used herein to refer to such surfaces, displays, or devices that are configured to detect the touch of a stylus and/or a non-stylus object.
Generally, touch sensitive, capacitive, or electromagnetic sensitive display surfaces lack good imaging resolution, inadequately distinguish shape and orientation of objects, and are deficient in sensing multiple objects in contact with the display surface at one time. Also, a pressure sensitive display surface requires actual contact with the display surface and cannot respond to objects that are in proximity with the display surface. Accordingly, it would be desirable for an interactive display device to respond to specific gestures made with the user's finger(s) or other objects that are detected by the interactive display device.